1. Field of the Invention
The present invention relates to a radar sensor, e.g., a radar sensor for distance measurement in a motor vehicle.
2. Description of the Related Art
In a motor vehicle, a radar sensor may be used for determining a distance to a surrounding object. Based on the determined distance, different comfort and convenience functions of the motor vehicle may be controlled. For example, a speed of the motor vehicle may be automatically controlled to a predetermined value, a forward distance measurement with the aid of the radar sensor ensuring that the vehicle maintains a predetermined safety distance to a preceding motor vehicle. Other applications of a radar sensor include an emergency brake function when rapidly approaching an object, a distance warning device for making it easier for a driver of the motor vehicle to maintain a safety distance to a preceding vehicle, or a parking assistant for collision warning in close range at a low driving speed.
Such radar sensors are generally designed as an integrated module, the module providing already evaluated or partially evaluated distance or proximity signals to an electrical interface. All components, which are necessary for transmitting, receiving and correlating radar signals, are included in the module.
Such a radar sensor generally includes a radar antenna, a high-frequency circuit for activating the radar antenna and a radar lens for focusing the radar radiation emitted by the radar antenna or radar radiation incident on it. To prevent high-frequency radiation of the radar antenna from adversely affecting the high-frequency circuit or high-frequency radiation of the high-frequency circuit from adversely affecting the function of the radar antenna, it is known to provide a metal plate or a metal cage, which includes a recess, through which the radar antenna transmits or receives radar radiation, to shield the radar antenna from the high-frequency circuit. This makes it possible to shield electromagnetic radiation and in particular the high-frequency radar radiation, so that the high-frequency circuit and the radar antenna do not mutually influence one another; however, this may also adversely affect the performance or characteristics of the radar antenna.
The object of the present invention is to suppress stray radiation in the area of a radar antenna of a radar sensor.